Airlines are urging travellers to arrive two hours before domestic flights and three hours before international flights.

Australia announced tougher security processes at major airports after police stopped an alleged terror plot in Sydney on Saturday (29 July).

Qantas, Tiger, and Virgin Australia are advising travellers to limit carry-on and checked baggage to reduce delays in screening.

They are also urging travellers to arrive two hours before domestic flights and three hours before international flights.

Authorities are taking extra precaution with additional checks of cabin and checked baggage at the airports of Sydney, Melbourne, Brisbane, Darwin, Hobart, Perth, Adelaide, Canberra, Cairns and the Gold Coast.

"All Australian airports have been asked to exercise increased vigilance in their security operations, including at security screening points and within the terminal area," Darren Chester, transport minister said.

"As a matter of course, the Australian government will continue to monitor security developments and adjust security settings as needed," he added.

According to ABC, the impact of the new arrangements at Sydney airport are causing a waiting time of up to 90 minutes.

A number of users on even praised Qantas and Sydney airport workers on social media for getting passengers through quickly.

On Saturday, the police had raided five properties across Sydney and arrested four men who are yet to be charged.

Andrew Colvin, Australian federal police commissioner during a press conference with Prime Minister Malcolm Turnbull on Sunday said that airport security had been compromised, but described the plot as credible.

"In recent days, law enforcement has become aware of information that suggested some people in Sydney were planning to commit a terrorist act using an improvised device," Colvin said.

"We do believe it is Islamic-inspired terrorism. Exactly what is behind this is something that we will need to investigate fully. At this time we don't have a great deal of information on the specific attack, the location, date or time. However, we are investigating information indicating that the aviation industry was potentially a target ..." he added.